Super Mario Bros. 3 graphics and sound (Southbird's disassembly)

Each frame the NMI handler loads the MMC3's scanline counter with 192, and the IRQ it raises points the PPU at the status bar's nametable rows and swaps in the status bar's tile banks. smb3-av/irq-status-bar

About: Super Mario Bros. 3 Status bar split

Value: 192 scanlines

The MMC3 counts rendered scanlines (nes-hardware/mmc3-irq), so the count of 192 is the split's line; the status bar fills the rows below it.

Cited by: Status bar split

At the status bar the IRQ handler switches the background's two 2 KB CHR banks to the status bar's tiles and all four 1 KB sprite banks to blank tiles, so no sprite shows over the bar. smb3-av/status-bar-banks

About: Super Mario Bros. 3 CHR bank switching

Cited by: CHR bank switching

In ordinary levels the game picks the 2 KB background bank at PPU $0800 from PT2_Anim, banks $60, $62, $64, $66, by frame-counter bits 3-4, so the animated tiles step every 8 frames on a 32-frame loop; an active P-Switch forces bank $3E. smb3-av/tile-animation

About: Super Mario Bros. 3 CHR bank switching

{
 "banks": [
  96,
  98,
  100,
  102
 ],
 "framesPerStep": 8,
 "loopFrames": 32,
 "ppuAddress": "$0800",
 "bankKB": 2,
 "pSwitchBank": 62
}

Airship levels step their own banks from $70 to $74 every 4 frames instead (PRG/prg030.asm, just above). Which tiles the banks animate (question blocks, coins, water) was not read from the CHR data.

Cited by: CHR bank switching

In the N-Spade card game three IRQs, at scanlines 32, 84, and 136, each give one row its own horizontal scroll and set the next IRQ 52 lines on, and a fourth restores the status bar, so three bands of the screen slide independently. smb3-av/spade-raster

About: Super Mario Bros. 3 Raster effects

{
 "firstLine": 32,
 "rowGap": [
  52,
  52,
  52
 ],
 "rows": 3
}

Raster state 3 restores the status bar's banks and scroll. That the game is the N-Spade card-matching game is the disassembly's label (UPDATERASTER_SPADEGAME, "Spade Bonus Game (3 sliding rows)" in smb3.asm), not a probe.

Cited by: Raster effects

The music data has a sample track beside the other channels' tracks; each note byte on it queues a sample, and Music_PlayDMC loads that sample's rate, address, and length from three 16-entry tables and restarts the DMC. smb3-av/dmc-track

About: Super Mario Bros. 3 DPCM samples

The 16 sample entries play 9 recordings, some reused at a lower rate or cut short; their rate bytes are $0F (33,144 Hz) for most, and $0E (24,858 Hz) or $0D (21,307 Hz) for some of the reused copies. smb3-av/dmc-samples

About: Super Mario Bros. 3 DPCM samples

{
 "entries": 16,
 "recordings": 9,
 "rates": [
  15,
  15,
  15,
  15,
  15,
  15,
  14,
  15,
  14,
  15,
  14,
  13,
  15,
  15,
  14,
  13
 ],
 "ratesHz": {
  "13": 21307,
  "14": 24858,
  "15": 33144
 }
}

Rates $F, $E, $D are 54, 72, and 84 CPU cycles per bit (nes-hardware/dmc). Southbird's comment marks entry 3 as a bad length that would play DMC02 "and just continue on through code". What each recording is (timpani, bongo, and so on) is not labeled in the disassembly.

Cited by: DPCM samples